In transurethral surgery, where a resectoscope is inserted through the urethra to remove that portion of the prostate gland (adenoma) which obstructs the urinary passage, the surgeon ordinarily uses a finger of his other hand to palpate and adjust the position of the prostate during cutting by pressing upwardly against the wall of the rectum. To avoid contamination of the gloved hand and surgical field generally, a drape is commonly used that is equipped with a sheath or cot intended to be inserted into the rectum and to remain in place throughout the operative procedure.
Although efforts have been made to develop urological drapes with cots which are self-retaining in use, such efforts have been generally unsuccessful. Thus, cots have been devised with external annular ribs in close proximity to the body portions of the drapes, presumably in the expectation that such a rib will engage and be retained by the anal sphincter. In practice, however, such retention has been found undependable. Problems may arise, for example, should the surgeon find it necessary to withdraw his finger from the cot and thereafter reinsert it -- an action which may normally occur many times during such an operation. With each withdrawal, there is a risk that the cot will also be extracted or expelled. Furthermore, should the surgeon's gloved finger stick to the inside surface of the natural or synthetic rubber cot, evagination of the cot is likely to occur as the finger is extracted, the cot there being everted and pulled from the patient, creating risks of contamination and otherwise complicating the operative procedure.
Transurethral prostatic resection is discussed in detail in texts such as R. M. Nesbit et al., Transurethral Prostatic Resection, Nelson's Loose-Leaf Surgery, 305-320 (1949, Thomas Nelson & Sons). Typical urological drapes are depicted and described in V. Mueller Catalog, 369 (1968). Other references illustrating the state of the prior art are U.S. Pat. Nos. 1,491,011, 2,123,343, and 2,406,600.